From the wreckage of the Trayvon Martin killing, the hoodie has emerged as an unlikely symbol, a silent way of expressing solidarity and anger over justice delayed as protests erupt nationwide over the death of an unarmed black teenager at the hands of a Central Florida neighborhood watch captain who viewed the boy as suspicious.

From a downtown outdoor mall in Iowa City to the expanse of Union Square in New York City, from a historic church in Atlanta to a plaza in Washington, D.C., thousands of demonstrators have been protesting the 17-year-old’s death by donning hoodies like the one Trayvon wore that Sunday night a month ago when he was killed in a gated townhouse community in Sanford. Thousands more have posted, shared and tweeted photos of themselves wearing the hooded jackets. Still others have used Trayvon’s haunting black-and-white image as their own profile pictures on the Internet, creating a boundless digital imprint in a case fueled by social media, the focus intensifying Friday with the release of a Miami Heat photo and a controversial remark by TV personality Geraldo Rivera.

“Before the incident, there was a cultural understanding that the African-American male wore hoodies as a way to be under the radar, to be ambiguous, but not because of any malicious intent, not because he was up to no good,’’ says Jason Campbell, an assistant professor of conflict resolution and philosophy at Nova Southeastern University. “Now, it’s visual shorthand that has transcended, used as a way to say I am lending my voice to the cause. It’s not a black cause, or a male cause, it’s a national cause.’’

Trayvon was wearing a hoodie — and carrying a bag of Skittles and an Arizona iced tea purchased from a nearby convenience store — as he returned to the townhouse of his father’s girlfriend. He had been suspended from high school in Miami and was spending time in Sanford with his father. The shooter, George Zimmerman, 28, told police the boy was wearing a dark hoodie, looked “suspicious” and thought he was “up to no good.’’ He said Trayvon jumped him and he shot in self-defense. The boy died on the grass, 70 yards from the backdoor of the townhouse. Trayvon’s girlfriend, who was on a cellphone with him moments before, said it was not until he noticed he was being followed by a stranger that he cloaked himself with the hood.

In the month since the boy’s Feb. 26 death, with no arrests made, a national social movement has grown, exposing the fault lines of race and exploring what it means to be young, black and wearing a hoodie.

The hooded jacket or pullover — an ubiquitous uniform for the youth, hip-hop and sports worlds, a sideline favorite of New England Patriot Coach Bill Belichick and a casual outfit for Facebook co-founder Mark Zuckerberg — has become a powerful part of the Trayvon Martin narrative. Ordinary citizens, political personalities, athletes and big-name celebrities have joined the cause, posting hooded images of themselves, people as disparate as Oscar winner Jamie Foxx; Marian Wright Edelman, who heads the Children’s Defense Fund; and former Michigan Gov. Jennifer Granholm. Many of the images included simple text, asking “Do I Look Suspicious?” or stating, “I am Trayvon.”

For the newly minted hoodie movement, the goal is both to protest Trayvon’s death and also to take back the clothing item, to remove the sting of its sometimes sinister image.

“The meaning has changed for me. Now, I am honored to wear my hoodie because it is showing respect toward Trayvon,’’ said Desrick Hudson, 17, a junior at Norland Senior High who went to elementary and middle school with Trayvon.

The Miami-Dade school district allows hoodies as long as the hood remains down so that students can be easily identified.

“I wore them to school as a fashion thing, no different than putting on a hat,’’ Desrick said. “Now it means something bigger.’’

The hoodie discourse exploded Friday after Fox News personality Geraldo Rivera asserted that the hoodie — and Trayvon’s decision to wear it — was a factor in his shooting death, comments that drew fiery responses from the social media world, including from his own son.

“I believe that George Zimmerman, the overzealous neighborhood watch captain, should be investigated to the fullest extent of the law and if he is criminally liable, he should be prosecuted,’’ Rivera said Friday morning on Fox & Friends. “But I am urging the parents of black and Latino youngsters, particularly, to not let their children go out wearing hoodies. I think the hoodie is as much responsible for Trayvon Martin’s death as George Zimmerman was.’’

He said the hoodies, first produced by clothing company Champion in the 1930s for laborers working in the New York winters, have become a menacing symbol of criminality. Merely wearing one forced people to respond, he said, adding that the image of a black or Latino male in a hoodie is so provocative, the clothing should come with a warning label, like cigarettes — “caution, wearing this could get you killed.”

“When you see a black or Latino youngster, particularly on the street, you walk to the other side of the street. You try to avoid that confrontation. Trayvon Martin you know, God bless him, he’s an innocent kid, a wonderful kid, a box of Skittles in his hand. He didn’t deserve to die,’’ Rivera said. “But I’ll bet you money, if he didn’t have that hoodie on, that — that nutty neighborhood watch guy wouldn’t have responded in that violent and aggressive way.’’

Rivera, who is Hispanic, admitted over Twitter that his son, Gabriel, was “ashamed” of the stance he has taken on wearing hoodies.

Trayvon’s death and his choice of clothing have renewed the focus on the never-ending conversation about race and stereotypes and the inherent difficulties of being a black male.

“The country is following the narrative of George Zimmerman. He tells 911 he sees someone who is suspicious. So what do we know about Trayvon? He was wearing jeans, tennis shoes and a hoodie. Somehow, Zimmerman arrives at the notion that because he is wearing this hoodie, he is suspicious,’’ says journalist Roland Martin, host of TV One’s Washington Watch and author of Speak, Brother! A Black Man’s View of America. “The reason the hoodie is so important in this narrative, is it is a symbolic piece of clothing that speaks to the stereotypes people carry.’’

Martin, who also is a CNN contributor, said the case is weighed down by institutional racism and age-old assumptions.

“If I see a white kid in a hoodie or a dark trench coat and tattoos, I do not think he is a skinhead. If I see a white guy on Wall Street in a suit, I don’t automatically think he is a white-collar criminal. And if I see a Hispanic person speaking Spanish instead of English, I don’t assume they are an illegal alien,’’ he said. “Hoodies are deeply entrenched in American culture, not just urban culture, so the problem is not the hoodie. it’s the person who carries the stereotype that hoodies represent a black or Hispanic up to no good.’’

On Friday, Heat star Dwyane Wade posted an old photo of himself on Facebook in a hoodie to show support for the Martin family. While in town for that night’s game against the Detroit Pistons, LeBron James also tweeted a stark photograph of himself and 12 other teammates including Wade, heads dropped, faces shadowed by dark hooded sweatshirts, evoking an almost monk-like image. The point, perhaps, is to change the perception of the clothing item from dangerous to sacred. The photo, posted to James’ Twitter account — he is followed by four million people — was taken at the Heat’s team hotel in Birmingham, Mich., meant to demonstrate the team was united in the battle for justice.

“I’m a father. It’s support of the tragic thing that has taken place. No matter what color, race, we’re all fathers,’’ Wade told the Sun Sentinel. “When you think about what that family’s going through, it hits you hard and it hurts your heart to think about it. Just anything you can do, obviously we can’t bring him back, but anything you can do to get behind and support is what we’re doing.’’